Liqueurs are historical descendants of herbal medicines; they were made in Italy as early as the 13th century and were often prepared by monks.
Some liqueurs are prepared by infusing certain woods, fruits, or flowers in either water or alcohol and adding sugar or other items. Others are distilled from aromatic or flavoring agents. Anise liqueurs have the interesting property of turning from transparent to cloudy when added to water: the oil of anise remains in solution in the presence of a high concentration of alcohol, but crystallizes when the alcohol concentration is reduced; this is known as the ouzo effect.
Nowadays, liqueurs are made worldwide and are served in many ways: by themselves, poured over ice, with coffee, mixed with cream or to create cocktails, etc. They are often served with or after a dessert. Liqueurs are also used in cooking.